Implant tools with attachment feature and multi-positional sheath and implant techniques utilizing such tools

ABSTRACT

Implant tools and techniques for implantation of a medical lead, catheter or other implantable component are provided. The implant tools and techniques are particularly useful in implanting medical electrical leads in extravascular locations, including subcutaneous locations. An example implant tool for implanting a medical lead includes a rod and a sheath configured to be placed on the rod. The rod includes a handle, a shaft having a proximal end adjacent to the handle and a distal end, and an attachment feature toward the distal end of the shaft, the attachment feature configured to couple to the medical lead. The sheath is configured to be placed in multiple positions along the rod including a first position in which the sheath does not interact with the attachment feature and second position in which the sheath does interact with the attachment feature.

This application claims the benefit of U.S. Provisional Application No.61/903,139, filed on Nov. 12, 2013, the content of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to implant tools and techniques forimplanting medical leads or other implantable components inextravascular locations.

BACKGROUND

Implantable cardiac defibrillator (ICD) systems are used to deliver highenergy electrical pulses or shocks to a patient's heart to terminatelife threatening arrhythmias, such ventricular fibrillation. TraditionalICD systems include a housing that encloses a pulse generator and otherelectronics of the ICD and is implanted subcutaneously in the chest ofthe patient. The housing is connected to one or more implantable medicalelectrical leads that are implanted within the heart.

Traditional ICD systems that utilize transvenous leads may not be thepreferable ICD system for all patients. For example, some patients withdifficult vascular access precludes placement of transvenous leads. Asanother example, children and other younger patients may also candidatesfor non-transvenous ICD systems. Moreover, transvenous leads may becomefibrosed in the heart over time, making lead revision and extractionprocedures challenging.

A subcutaneous ICD system may be preferred for these patients. Asubcutaneous ICD system includes a lead (or leads) that are implantedsubcutaneously in the patient, i.e., between the skin and the ribsand/or sternum of the patient. As such, the subcutaneous ICD mayeliminate the need to transvenous leads within the heart.

SUMMARY

This disclosure provides implant tools and techniques for implantationof a medical lead, catheter or other component, in extravascularlocations including subcutaneous locations. In one example, thisdisclosure provides an implant tool for implanting a medical lead. Theimplant tool comprises a rod and a sheath configured to be placed on therod. The rod includes a handle, a shaft having a proximal end adjacentto the handle and a distal end, and an attachment feature toward thedistal end of the shaft, the attachment feature configured to couple tothe medical lead. The sheath includes a body having proximal end and adistal end, and further wherein the sheath is configured to be placed inmultiple positions along the rod including a first position in which thesheath does not interact with the attachment feature and second positionin which the sheath does interact with the attachment feature.

In another example, this disclosure provides a method for implanting amedical electrical lead using a rod having a handle, a shaft having aproximal end adjacent to the handle and a distal end, and an attachmentfeature toward the distal end of the shaft, the attachment featureconfigured to couple to the medical lead, and a sheath configured to beplaced on the shaft of the rod, the sheath having body defining achannel, the medical electrical lead having a proximal end including aconnector mechanism configured to connect to an implantable medicaldevice and a distal end including one or more electrodes.

The method comprises creating a first incision at a first location on atorso of a patient, creating a second incision at a second location onthe torso of the patient, introducing the rod, with the sheath placed onthe rod at a first position in which the sheath does not interact withthe attachment feature of the rod, into the patient via the firstincision, advancing the rod from the first incision to the secondincision to create a first path between the first incision and thesecond incision, attaching an attachment feature of the medicalelectrical lead to the attachment feature of the rod, advancing thesheath to a second position in which the sheath does interact with theattachment feature of the rod after attaching the attachment feature ofthe medical electrical lead to the attachment feature of the rod,withdrawing the rod from the patient to pull the medical electrical leadalong the path between the first incision to the second incision,retracting the sheath to the first position such that the sheath nolonger interacts with the attachment feature of the rod, and removingthe attachment feature of the medical electrical lead from theattachment feature of the rod.

This summary is intended to provide an overview of the subject matterdescribed in this disclosure. It is not intended to provide an exclusiveor exhaustive explanation of the techniques as described in detailwithin the accompanying drawings and description below. Further detailsof one or more examples are set forth in the accompanying drawings andthe description below. Other features, objects, and advantages will beapparent from the description and drawings, and from the statementsprovided below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a patient implanted with an exampleextravascular cardiac defibrillation system.

FIGS. 2A and 2B are conceptual drawings illustrating an exampleextravascular implant tool.

FIGS. 3A-3E are conceptual drawings illustrating various views of anexample open sheath of FIGS. 2A and 2B in further detail.

FIGS. 4A and 4B illustrate example alternative cross-sections of adistal end of an open sheath.

FIG. 5 illustrates an angled view of a distal end of an examplesplittable sheath.

FIG. 6 illustrates an angled view of a distal end of an exampleslittable sheath.

FIGS. 7A and 7B illustrate a distal end of an implant tool beingattached to an implantable medical lead.

FIGS. 8A-I illustrate an example method of implanting an implantablemedical lead using an implant tool in accordance with this disclosure.

FIGS. 9A-9I illustrated another example method of implanting animplantable medical lead using an implant tool in accordance with thisdisclosure.

FIG. 10 illustrates an example of an implant tool that includes a rodand a sheath having a multi-positional handle.

FIG. 11 illustrates an enlarged view of the handle of the sheath of FIG.10.

FIGS. 12A and 12B illustrate the placement of the sheath having amulti-positional handle in two positions on the rod of the implant toolof FIG. 10.

FIGS. 13A and 13B illustrates a distal end of an alternative attachmentfeature of a rod.

FIG. 14 illustrates a distal portion of another example rod.

FIG. 15 illustrates a distal portion of another example rod.

DETAILED DESCRIPTION

FIG. 1 is a conceptual diagram illustrating a patient 12 implanted withan example extravascular cardiac defibrillation system 10. In theexample illustrated in FIG. 1, extravascular cardiac defibrillationsystem 10 is an implanted subcutaneous defibrillation system. However,the implant tools and techniques of this disclosure may also be utilizedwith other extravascular implanted cardiac defibrillation systems, suchas a cardiac defibrillation system having a lead implanted at leastpartially in a substernal or submuscular location. Additionally, theimplant tools and techniques of this disclosure may also be utilizedwith other implantable cardiac systems, such as implantable cardioverterdefibrillator systems, implantable cardiac resynchronization therapy(CRT) systems (e.g., CRT-P or CRT-D systems), implantable pacingsystems, other implantable cardiac systems that include combinations ofthe cardiac systems above. Likewise the techniques may be used innon-cardiac implantable systems, including in, implantableneurostimulation systems, drug delivery systems or other systems inwhich leads, catheters or other components are implanted atextravascular locations within patient 12. This disclosure, however, isdescribed in the context of an implantable extravascular cardiacdefibrillation system for purposes of illustration.

Extravascular cardiac defibrillation system 10 includes an implantablecardiac defibrillator (ICD) 14 connected to at least one implantablecardiac defibrillation lead 16. ICD 14 of FIG. 1 is implantedsubcutaneously on the left side of patient 12. Defibrillation lead 16,which is connected to ICD 14, extends medially from ICD 14 towardsternum 28 and xiphoid process 24 of patient 12. At a location nearxiphoid process 24 defibrillation lead 16 bends or turns and extendssubcutaneously superior, substantially parallel to sternum 28. In theexample illustrated in FIG. 1, defibrillation lead 16 is implanted suchthat lead 16 is offset laterally to the left side of the body of sternum28 (i.e., towards the left side of patient 12).

Defibrillation lead 16 is placed along sternum 28 such that a therapyvector between defibrillation electrode 18 and a second electrode (suchas a housing or can electrode of ICD 14 or an electrode placed on asecond lead) is substantially across the ventricle of heart 26. Thetherapy vector may, in one example, be viewed as a line that extendsfrom a point on the defibrillation electrode 18 to a point on thehousing or can electrode of ICD 14. In another example, defibrillationlead 16 may be placed along sternum 28 such that a therapy vectorbetween defibrillation electrode 18 and a housing or can electrode ofICD 14 (or other electrode) is substantially across an atrium of heart26. In this case, extravascular ICD system 10 may be used to provideatrial therapies, such as therapies to treat atrial fibrillation.

The embodiment illustrated in FIG. 1 is an example configuration of anextravascular cardiac defibrillation system 10 and should not beconsidered limiting of the techniques described herein. For example,although illustrated as being offset laterally from the midline ofsternum 28 in the example of FIG. 1, defibrillation lead 16 may beimplanted such that lead 16 is offset to the right of sternum 28 or oversternum 28. Additionally, defibrillation lead 16 may be implanted suchthat it is not substantially parallel to sternum 28, but instead offsetfrom sternum 28 at an angle (e.g., angled lateral from sternum 28 ateither the proximal or distal end). As another example, the distal endof defibrillation lead 16 may be positioned near the second or third ribof patient 12. However, the distal end of defibrillation lead 16 may bepositioned further superior or inferior depending on the location of ICD14, location of electrodes 18, 20, and 22, or other factors.

Although ICD 14 is illustrated as being implanted near a midaxillaryline of patient 12, ICD 14 may also be implanted at other subcutaneouslocations on patient 12, such as further posterior on the torso towardthe posterior axillary line, further anterior on the torso toward theanterior axillary line, in a pectoral region, or at other locations ofpatient 12. In instances in which ICD 14 is implanted pectorally, lead16 would follow a different path, e.g., across the upper chest area andinferior along sternum 28. When the ICD 14 is implanted in the pectoralregion, the extravascular ICD system may include a second lead includinga defibrillation electrode that extends along the left side of thepatient such that the defibrillation electrode of the second lead islocated along the left side of the patient to function as an anode orcathode of the therapy vector of such an ICD system.

ICD 14 includes a housing that forms a hermetic seal that protectscomponents within ICD 14. The housing of ICD 14 may be formed of aconductive material, such as titanium, titanium alloy, or otherbiocompatible conductive material or a combination of conductive andnon-conductive materials. In some instances, the housing of ICD 14functions as an electrode (sometimes referred to as a housing electrodeor can electrode) that is used in combination with one of electrodes 18,20, or 22 to deliver a therapy to heart 26 or to sense electricalactivity of heart 26. ICD 14 may also include a connector assembly(sometimes referred to as a connector block or header) that includeselectrical feedthroughs through which electrical connections are madebetween conductors within defibrillation lead 16 and electroniccomponents included within the housing. The housing may enclose one ormore components, including processors, memories, transmitters,receivers, sensors, sensing circuitry, therapy circuitry and otherappropriate components (often referred to herein as modules).

Defibrillation lead 16 includes a lead body having a proximal end thatincludes a connector configured to connect to ICD 14 and a distal endthat includes one or more electrodes 18, 20, and 22. The lead body ofdefibrillation lead 16 may be formed from a non-conductive material,including silicone, polyurethane, fluoropolymers, mixtures thereof, andother appropriate materials, and shaped to form one or more lumenswithin which the one or more conductors extend. However, the techniquesare not limited to such constructions. Although defibrillation lead 16is illustrated as including three electrodes 18, 20 and 22,defibrillation lead 16 may include more or fewer electrodes.

Defibrillation lead 16 includes one or more elongated electricalconductors (not illustrated) that extend within the lead body from theconnector on the proximal end of defibrillation lead 16 to electrodes18, 20 and 22. In other words, each of the one or more elongatedelectrical conductors contained within the lead body of defibrillationlead 16 may engage with respective ones of electrodes 18, 20 and 22.When the connector at the proximal end of defibrillation lead 16 isconnected to ICD 14, the respective conductors may electrically coupleto circuitry, such as a therapy module or a sensing module, of ICD 14via connections in connector assembly, including associatedfeedthroughs. The electrical conductors transmit therapy from a therapymodule within ICD 14 to one or more of electrodes 18, 20 and 22 andtransmit sensed electrical signals from one or more of electrodes 18, 20and 22 to the sensing module within ICD 14.

ICD 14 may sense electrical activity of heart 26 via one or more sensingvectors that include combinations of electrodes 20 and 22 and a housingor can electrode of ICD 14. For example, ICD 14 may obtain electricalsignals sensed using a sensing vector between electrodes 20 and 22,obtain electrical signals sensed using a sensing vector betweenelectrode 20 and the conductive housing or can electrode of ICD 14,obtain electrical signals sensed using a sensing vector betweenelectrode 22 and the conductive housing or can electrode of ICD 14, or acombination thereof. In some instances, ICD 14 may even sense cardiacelectrical signals using a sensing vector that includes defibrillationelectrode 18, such as a sensing vector between defibrillation electrode18 and one of electrodes 20 or 22, or a sensing vector betweendefibrillation electrode 18 and the housing or can electrode of ICD 14.

ICD may analyze the sensed electrical signals to detect tachycardia,such as ventricular tachycardia or ventricular fibrillation, and inresponse to detecting tachycardia may generate and deliver an electricaltherapy to heart 26. For example, ICD 14 may deliver one or moredefibrillation shocks via a therapy vector that includes defibrillationelectrode 18 of defibrillation lead 16 and the housing/can electrode.Defibrillation electrode 18 may, for example, be an elongated coilelectrode or other type of electrode. In some instances, ICD 14 maydeliver one or more pacing therapies prior to or after delivery of thedefibrillation shock, such as anti-tachycardia pacing (ATP) or postshock pacing. In these instances, ICD 14 may generate and deliver pacingpulses via therapy vectors that include one or both of electrodes 20 and22 and/or the housing/can electrode. Electrodes 20 and 22 may comprisering electrodes, hemispherical electrodes, coil electrodes, helixelectrodes, segmented electrodes, directional electrodes, or other typesof electrodes, or combination thereof. Electrodes 20 and 22 may be thesame type of electrodes or different types of electrodes, although inthe example of FIG. 1 both electrodes 20 and 22 are illustrated as ringelectrodes.

Defibrillation lead 16 may also include an attachment feature 29 at ortoward the distal end of lead 16. The attachment feature 29 may be aloop, link, or other attachment feature. For example, attachment feature29 may be a loop formed by a suture. As another example, attachmentfeature 29 may be a loop, link, ring of metal, coated metal or apolymer. The attachment feature 29 may be formed into any of a number ofshapes with uniform or varying thickness and varying dimensions.Attachment feature 29 may be integral to the lead or may be added by theuser prior to implantation. Attachment feature 29 may be useful to aidin implantation of lead 16 and/or for securing lead 16 to a desiredimplant location. In some instances, defibrillation lead 16 may includea fixation mechanism in addition to or instead of the attachmentfeature. Although defibrillation lead 16 is illustrated with anattachment feature 29, in other examples lead 16 may not include anattachment feature 29. In this case, defibrillation lead 16 may beconnected to or secured to an implant tool via an interference fit aswill be described in more detail herein. An interference fit, sometimesalso referred to as a friction fit, is a fastening between two partswhich is achieved by friction after the parts are pushed together,rather than by any other means of fastening.

Lead 16 may also include a connector at the proximal end of lead 16,such as a DF4 connector, bifurcated connector (e.g., DF-1/IS-1connector), or other type of connector. The connector at the proximalend of lead 16 may include a terminal pin that couples to a port withinthe connector assembly of ICD 14. In some instances, lead 16 may includean attachment feature at the proximal end of lead 16 that may be coupledto an implant tool to aid in implantation of lead 16. In one example, aportion of the connector at the proximal end of lead 16 may be utilizedas the attachment feature. In another example, the attachment feature atthe proximal end of the lead may separate from the connector and may beeither integral to the lead or added by the user prior to implantation.

Defibrillation lead 16 may also include a suture sleeve or otherfixation mechanism (not shown) located proximal to electrode 22 that isconfigured to fixate lead 16 near the xiphoid process or lower sternumlocation. The fixation mechanism (e.g., suture sleeve or othermechanism) may be integral to the lead or may be added by the user priorto implantation.

The example illustrated in FIG. 1 is exemplary in nature and should notbe considered limiting of the techniques described in this disclosure.For instance, extravascular cardiac defibrillation system 10 may includemore than one lead. In one example, extravascular cardiac defibrillationsystem 10 may include a pacing lead in addition to defibrillation lead16.

In the example illustrated in FIG. 1, defibrillation lead 16 isimplanted subcutaneously, e.g., between the skin and the ribs and/orsternum. In other instances, defibrillation lead 16 (and/or the optionalpacing lead) may be implanted at other extravascular locations. In oneexample, defibrillation lead 16 may be implanted at least partially in asubsternal location. In such a configuration, at least a portion ofdefibrillation lead 16 may be placed under/below the sternum in themediastinum and, more particularly, in the anterior mediastinum. Theanterior mediastinum is bounded laterally by pleurae, posteriorly bypericardium, and anteriorly by sternum. Defibrillation lead 16 may be atleast partially implanted in other extra-pericardial locations, i.e.,locations in the region around, but not in direct contact with, theouter surface of heart 26. These other extra-pericardial locations mayinclude in the mediastinum but offset from sternum 28, in the superiormediastinum, in the middle mediastinum, in the posterior mediastinum, inthe sub-xiphoid or inferior xiphoid area, near the apex of the heart, orother location not in direct contact with heart 26 and not subcutaneous.In still further instances, the implant tools described herein may beutilized to implant the lead at a pericardial or epicardial locationoutside the heart 26. Moreover, implant tools such as those describedherein may be used to implant non-cardiac leads in other locationswithin patient 12.

FIGS. 2A and 2B are conceptual drawings illustrating an exampleextravascular implant tool, which includes components for implanting amedical lead, such as lead 16 of FIG. 1, a catheter, or otherimplantable component. The implant tool includes a rod 30 and a sheath50. As will be described in further detail herein, the implant tool ofFIGS. 2A and 2B may be particularly useful in implanting defibrillationlead 16 in patient 12 in a subcutaneous, substernal, or otherextravascular location.

Rod 30 includes a handle 32 at a proximal end of rod 30 and an elongateshaft 34 that extends from handle 32 to a distal end of rod 30. Thedistal end of rod 30 of elongate shaft 34 may be shaped to aid intunneling through subcutaneous or other tissue, muscle, ligament orbodily structure. For example, the distal end of the elongate shaft 34may be blunt, rounded, tapered, pointed or otherwise shaped to enable auser to tunnel through subcutaneous or other tissue without excessdamage to surrounding tissue, piercing through the skin, or coring ofthe tissue. In some instances, the distal end of rod 30 may be bent orcurved, which may aid in tunneling under sternum 28. In particular thebend or shape may be oriented toward the sternum and follow along theunderside of the sternum to reduce the likelihood of damage to thepleural or pericardium or other structure.

Elongate shaft 34 of rod 30 is formed such that it is stiff enough to becapable of being pushed through the tissue, muscle or other structure toform a path through the body. Shaft 34 may be made of a metal, alloy,polymer, or other material or combination of materials. In someinstances, such as when shaft 34 is made of metal or alloy, shaft 34 maybe malleable. For example, a user of rod 30 may form shaft 34 to achievea desired shape or bend. In this case, an implant kit may include thetool (e.g., rod 30 and sheath 50) as well as a bending tool (notillustrated in FIGS. 2A and 2B) to aid the user in forming the tool tothe desired shape or with the desired bend. However, rod 30 may beformed by the user without a designated bending tool. In otherinstances, the implant tool may include a pre-formed or pre-shaped rodhaving a curve or bend toward a distal end of shaft. Alternatively,shaft 34 may not be malleable, such as when shaft 34 is formed from apolymer. Even when shaft 34 is not malleable, however, shaft 34 may besomewhat flexible while still being stiff enough to tunnel throughtissue. The flexibility may allow a user to manipulate the tool slightlyto control direction (e.g., steer) of the tunnel. For example, adownward or upward force applied near the distal end of handle 32 (e.g.,adjacent to shaft 34) may result in shaft 34 flexing such that thedistal end of shaft 34 is directed upward or downward, respectively.Similarly, a force applied in to the left or right near the distal endof handle 32 may result in shaft 34 flexing such that the distal end ofshaft 34 is directed right or left, respectively.

Handle 32 of rod 30 may also be made of a metal, alloy, polymer, orother material or combination of materials. Handle 32 and elongate shaft34 may, in some instances, be constructed of the same material. Forexample, rod 30 may be formed of a single, unitary piece of material,such as a molded metal or rigid polymer. In other instances, handle 32and elongate shaft 34 may be constructed of different materials. In thiscase, handle 32 and shaft 34 may be formed of separate components thatare attached together to form rod 30, e.g., via a two piececonstruction. For example, handle 32 may be made of polymer and shaft 34may be made of metal and attached to handle 32 to form rod 30. Examplemetals or alloys from which handle 32 or shaft 34 may be constructedinclude, but are not limited to, stainless steel, titanium, titaniumalloys, nickel-cobalt, and nickel-cobalt alloys. Example polymers mayinclude, but are not limited to, acetal (e.g., DELRIN®), Polyether etherketone (PEEK), polycarbonate, polypropylene composites, andliquid-crystal polymer (LCP).

Rod 30 also includes an attachment feature toward the distal end ofelongate shaft 34. In the example illustrated in FIGS. 2A and 2B, theattachment feature is illustrated as a hook feature 36. In otherinstances, hook feature 36 may be located further distal along elongateshaft 34. Hook feature 36 is a mechanism by which rod 30 may attach to amedical electrical lead, e.g., via an attachment feature 29 of lead 16.For example, attachment feature 29 (e.g., suture, loop or the like) oflead 16 may be placed within hook feature 36 such that lead 16 may bepulled through a path in the tissue of patient 12 as rod 30 is withdrawnfrom the body of patient 12.

In the example illustrated in FIG. 2A, hook feature 36 is in-line withshaft 34. In other words, the outer diameter of shaft 34 distal to hookfeature 36 is approximately the same as the outer diameter of shaft 34proximal to hook feature 36. In other instances, however, hook feature36 may not be in-line, in which case, the outer diameter of shaft 34distal to hook feature 36 is smaller than the outer diameter of shaft 34proximal to hook feature 36 or the outer diameter of shaft 34 distal tohook feature 36 is greater than the outer diameter of shaft 34 proximalto hook feature 36.

Hook feature 36 may be formed in a number of different manners. In oneexample, hook feature 36 may be an angled slot across a bottom portionof shaft 34 with deburred edges. As illustrated in the enlarged view ofhook feature 36, shaft 34 defines a groove 40 that extends into shaft 34and toward the distal end of shaft 34. In particular, shaft 34 includesa lead-in 41 that tapers into shaft 34 and toward a distal end of shaft34, a bend 42 that curves to form the bowl of groove 40, and a lip 43.Lip 43 may be designed to be rounded or tapered to avoid catching ontissue or muscle when rod 30 is retracted or removed from body ofpatient 12. The shape of lip 43, radius of curvature of lip 43, or othercharacteristic of lip 43 may be selected or designed to reduce theamount of resistance hook feature 36 presents during retraction orremoval of rod 30 from patient 12. The distance 44 from the mostproximal portion of lip 43 to the most proximal portion of lead-in 41may also be selected or designed to be large enough to receiveattachment feature 29 of lead 16, but small enough to reduce thelikelihood of catching tissue or muscle during removal of rod 30 frompatient 12.

Although the attachment feature of rod 30 is illustrated as a hook 36 inFIG. 2A, the attachment feature may be formed as other features that maybe used to couple to a feature on a lead to pull the lead through asubcutaneous path within patient 12. In another embodiment, theattachment feature may be a formed to receive a particular portion of alead. For example, the attachment feature may be formed to receive aterminal pin of the connector at the proximal end of lead 16. In thiscase, the terminal pin of the connector of the lead may be placed withinthe attachment feature. Such an embodiment is described in furtherdetail with respect to FIGS. 13A and 13B.

Groove 40 has a width 44, depth 45 and throat 46. The size of width 44,depth 45 and throat 46 of groove 40 may be designed based on the type ofattachment feature 29 of lead 16 expected to be implanted using rod 30.For example, throat 46 may be much smaller such that it is just deepenough to catch a suture. Groove 40 of hook feature 36 is designed suchthat when rod 30 is being pulled, attachment feature 29 of lead 16 ispreferentially pulled into throat 46 of groove 40.

Rod 30 may include a stop 38 toward a proximal end of rod 30. In theexample illustrated in FIG. 2A, stop 38 is located at the point oftransition from shaft 34 to handle 32. In other examples, however, stop38 may be located further distal along shaft 34. In some instances, stop38 may be moveable.

Sheath 50 includes a body 52 having a proximal end and a distal end anda handle 54 located at the proximal end of body 52. In some instances,the distal end of body 52 may be tapered to aid in tunneling. Body 52 ofsheath 50 defines an inner channel. As will be described in furtherdetail below, sheath 50 may be an open sheath as illustrated anddescribed in further detail with respect to FIGS. 3A-E, 4A, and 4B. Inthe case of an open sheath, sheath 50 may include an opening along thelength of body 52 and the inner channel is accessible via the openinganywhere along the length of body 52. In another example, sheath 50 maybe a splittable sheath in which body 52 includes a score or otherweakened portion to permit splitting of body 52, e.g., as illustratedand described in further detail with respect to FIG. 5. In yet anotherexample, sheath 50 may be a sheath without any gap or score on body 52,in which case sheath 50 may be removed by slitting the sheath using aslitter, as illustrated and described in further detail with respect toFIG. 6.

Sheath 50 may be made of extruded or molded material. The material mayinclude, but not limited to, a polymer, a copolymer, a thermoplastic, orother material. Example materials include, but are not limited to,polyether block amide (such as PEBAX® 72D), polyether block amide blends(PEBAX® with a Foster ProPell™ additive), polyethylene,ultra-high-molecular-weight polyethylene (UHMWPE),Polytetrafluoroethylene (PTFE), nylons (such as GRILAMID® TR55 or L25,VESTAMID® L2140, AESNO®), or the like. In some instances, sheath 50 maybe made of multiple layers of different materials or may vary inmateriality and durometer along the length of body 52. For example,sheath 50 may be formed of PEBAX® with a PTFE lining the inner surfaceof the channel. Other additives or coatings that may be applied toincrease lubricity include, but are not limited to, siloxane, PTFE, andFoster ProPell™.

In some instances, rod 30 and/or sheath 50 may include markings (notshown in FIGS. 2A and 2B) that may aid the user during the implantprocedure. For example, the markings may provide the user feedbackregarding the distance tunneled or orientation of a shape and/or featureof rod 30. As another example, the markings may coincide with featureson lead 16. The markings may, for instance, coincide with electrodes 18,20 and 22, correspond with fixation mechanisms (such as a suture sleeveof lead 16), or other feature on lead 16. In instances in which themarkings coincide with features of lead 16, the user may utilize themarking prior to beginning the procedure to place landmarks on the skinof the patient. The user could then be more confident that when theinsertion tool is routed according to the landmarks that the electrodesor other lead features will be in the desired locations. The markingsmay be laser etched, printed, or otherwise placed on rod 30, sheath 50,or both.

FIG. 2B illustrates the implant tool formed by placing sheath 50 overrod 30. In some instances, sheath 50 may be sized such that sheath 50fits on shaft 34 of rod 30 in such a manner that an interference fit isachieved between sheath 50 and shaft 34 of rod 30. As described above,the interference fit is achieved by friction after the parts are pushedtogether, rather than by any other means of fastening. The interferencefit may, in some instances, be achieved by sizing and/or shaping the twomating parts so that one or the other, or both, slightly deviate in sizefrom the nominal dimension. The interference fit may therefore be viewedas referring to the fact that one part slightly interferes with thespace that the other is taking up. The tightness of the interference fitmay be controlled by the amount of allowance, e.g., the planneddifference from nominal size. Different allowances will result invarious strengths of fit. The value of the allowance depends on whichmaterial is being used, how big the parts are, and what degree oftightness is desired.

In one example, the diameter of the inner channel formed by body 52 ofsheath 50 may be equal to or slightly smaller than the outer diameter ofshaft 34 of rod 30. The allowance in this case may be on the order of1-10 thousandths of an inch. Allowances of less than 1 thousandth andgreater than 10 thousands may be used, however. As such, when placedover shaft 34 of rod 30, sheath 50 slightly expands in diameter causingthe interference fit. In some instances, the implant tool comprisingsheath 50 disposed over rod 30 may be used to pull a lead, such asdefibrillation lead 16, through a tunnel formed within tissue of patient12. In some cases, the interference fit may be tight enough to preventsheath 50 from being pulled off shaft 34 of rod 30 when being used topull lead 16 through the tunnel within patient 12. However, theinterference fit must also enable a user to easily place sheath 50 overshaft 34 of rod 30. Other techniques for achieving an interference fitmay also be utilized. In other embodiments described herein, handle 54of sheath 50 may be configured to retain sheath 50 in multiple positionson rod 30. This will be described in further detail with respect toFIGS. 10-13

In one embodiment, sheath 50 may have a length that is shorter than alength of shaft 34 of rod 30. In this manner, the distal end of shaft 34of rod 30 extends beyond the distal end of sheath 50. In the embodimentillustrated in FIG. 2B, body 52 of sheath 50 is short enough such thatwhen handle 54 of sheath 50 abuts against stop 38 of rod 30, hookfeature 36 of the distal end of rod 30 extends beyond the distal end ofsheath 50.

Rod 30 and sheath 50 may be sized based on the desired application. Rod30 may have diameter that is slightly larger than the diameter of thelead for which it will be used to implant, e.g., lead 16. In oneexample, rod 30 may have a diameter that is approximately one-half of aFrench larger than the diameter of lead 16. The implant tool may be usedto deliver leads of various sizes, such as 3-11 French leads (e.g.,1-3.7 mm leads). Sheath 50 may be sized to have an inner diameter (e.g.,the diameter of the inner surface of sheath 50) that is equal to orslightly less than the diameter of rod 30. In some instances the size ofsheath 50 may also be selected based on the diameter of the lead forwhich it will be used to implant. For example, sheath 50 may be sizedsuch that the inner diameter is slightly larger than the diameter of thelead.

FIGS. 3A-3E illustrate various views of an open sheath 60. Sheath 60 caninclude one or more of the structure and/or functionality of sheath 50(and vice versa). Repetitive description of like numbered elements inother embodiments is omitted for sake of brevity. Sheath 60 may, in oneexample, be used in conjunction with rod 30 in place of sheath 50.

3A illustrates a front view of sheath 60. 3B illustrates a top view ofsheath 60. As illustrated in the top view of FIG. 3B, sheath 60 includesan opening 62 that extends the entire length of body 62 from the distalend to the proximal end and through handle 61. As illustrated in FIG.3B, channel 64 is accessible via opening 62 anywhere along the length ofbody 63 from the proximal end to the distal end. In the exampleillustrated in FIG. 3B, opening 62 follows a substantially straight pathfrom the distal end of body 63 of sheath 60 to the proximal end of body63 of sheath 60. In alternative configurations, however, opening 62 mayfollow other paths from the distal end of body 63 to the proximal end ofbody 63, such as a spiral path or a meandering path.

FIGS. 3A and 3B illustrate sheath 60 having markings 65A-C(collectively, markings 65) that may aid the user during the implantprocedure. In the example, illustrated in FIGS. 3A and 3B, markings65A-C coincide with electrodes 18, 20 and 22, respectively, of lead 16when the distal end of lead 16 is aligned with the distal end of sheath60. In other instances, markings 65 may correspond with other featuresof lead 16, such as fixation mechanisms (e.g., an anchor sleeve of lead16). In instances in which the markings coincide with features of lead16, the user may utilize the marking prior to beginning the procedure toplace landmarks on the skin of patient 12. For example, prior tocreating incisions or prior to tunneling, the user may place the implanttool on the skin of patient 12 such that markings 65 coinciding with theelectrodes are located at a desired location, e.g., to achieve a desiredtherapy vector. The user may then place landmarks on the skin of patient12, such as landmarks corresponding with a desired end point of a tunnelor a desired tunneling path that places the features (e.g., electrodes18, 20, and 22) of lead 16 at the desired location. In this manner, theuser may use the markings on the implant tool to be more confident thatwhen rod 30 is routed according to the landmarks on the skin that theelectrodes or other lead features will be in the desired locations. Themarkings 65 may additionally or alternatively provide the user feedbackregarding the distance tunneled or orientation of a distal feature ofrod 30 (e.g., an orientation of a bend or curve at the distal end), inwhich case the markings may be located toward the proximal end of sheath60. Markings 65 may be laser etched, printed, or otherwise placed onsheath 60. Additionally or alternatively, similar markings may be madeon rod 30. In other instances, sheath 60 and rod 30 may not include anymarkings.

FIG. 3C illustrates a cross-sectional view of the distal end of sheath60 taken from B-B′. As illustrated in FIG. 3C, body 63 is C-shaped suchthat opening 62 defines a gap between end 67A and end 67B of body 63. Inother words, a gap exists between ends 67A and 67B along thecircumference or cross-section of body 63. Opening 62 may have a width“W1”. Body 63 defines a channel 64 that extends along the length of body63 from the distal end to the proximal end and through handle 61. Inthis case, channel 64 is a C-shaped channel, but the shape of channel 64may vary depending on the cross-sectional shape of body 63.

FIG. 3D illustrates a cross-sectional view of the proximal end of sheath60 taken from C-C′. As illustrated in FIG. 3D, body 63 has a similarC-shaped configuration such that the opening 62 defines a gap betweenend 68A and end 68B of body 63 such that channel 64 is accessible viaopening 62. Opening 62 at the proximal end of sheath 60 has a width“W2”. The proximal end of sheath 60 resides within a groove of handle 61such that handle 61 extends partially around the outer circumference ofbody 63. Handle 61 extends radially away from body 63 to provide a userof insertion tool the ability to grasp handle 61 to remove a lead fromchannel 64 or place sheath 60 over rod 30.

The widths W1 and W2 defined by opening 62 may vary in size. In someinstances, widths W1 and W2 are substantially the same size. Forexample, the width formed by opening 62 may be substantially the samewidth along the length of body 63. In another example, the width formedby opening 62 at the proximal and distal end may be the same, but thewidth toward a middle of body 63 of sheath 60 may be narrower. In otherinstances, widths W1 and W2 may have different widths such that thewidth formed by opening 62 may vary along the length of sheath 60. Forexample, width W1 at the distal end of sheath 60 may be narrower thanwidth W2 at the proximal end of sheath 60 such that lead 16 may be moreeasily inserted within channel 64. As another example, the width W1 atthe distal end of sheath 60 may be wider than width W2 at the proximalend of sheath 60.

FIG. 3E illustrates an angled view of the distal end of sheath 60. Body63 of sheath 60 forms inner channel 64 that extends the entire length ofbody 63 and through handle 61. Sheath 60 may be sized such that innerchannel 64 is equal to or slightly less than the outer diameter of rod30 yet allows for passage of a lead, such as defibrillation lead 16 ofFIG. 1 when sheath 60 is not disposed on shaft 34 of rod 30. Thus, thediameter of body 63 defining inner channel 64 may be sized to be equalto or slightly smaller than the outer diameter of shaft 34 of rod 30such that when placed on rod 30 an interference fit is achieved betweenshaft 34 and sheath 60. Sheath 60 may be formed to have a thickness 69that may vary depending on the type of material used to form sheath 60,the desired rigidity of sheath 60, or the like. Sheath 60 should berigid enough to not crumple, wrinkle, crease, or crush while beingtunneled through tissue of patient 12.

Opening 62 may vary in size depending upon the desired application.Opening 62 may be less than the diameter of lead 16. In one example,opening 62 may be approximately 10% less than the diameter of lead 16.However, in other examples, opening 62 may be less than 10% of thediameter of lead 16 or more than 10% of the diameter of lead 16. Opening62 may be larger or smaller than illustrated in FIGS. 3A-3E. FIGS. 4Aand 4B illustrate two example alternative cross-sections of a distal endof an open sheath.

FIG. 4A illustrates a cross-sectional view of the distal end of anexample body 70 of a sheath. Body 70 may correspond to body 63 of sheath60 of FIGS. 2 and 3 or any other sheath described herein and may includeone or more of the structure and/or functionality of body 63 of sheath60. As illustrated in FIG. 4A, body 70 has an opening 72 that defines agap between ends 71A and 71B. Body 70 may be generally viewed as beingc-shaped, horse-shoe shaped or semi-circle shaped defining a similarlyshaped channel 73. Opening 72 may have a width “W3” is equal to orslightly smaller than the diameter of lead 16. Opening 72 has a width W3that is larger in size than widths W1 and W2 of opening 62 of FIGS.3A-3E.

FIG. 4B illustrates a cross-sectional view of another example body 74 ofa sheath. Body 74 may correspond to body 63 of sheath 60 or any othersheath described herein and may include one or more of the structureand/or functionality of body 63 of sheath 60. As illustrated in FIG. 4C,body 74 extends around substantially the entire circumference such thatopening 76 defines only a small gap between the ends 78A and 78B of body74. As such, channel 79 formed by body 74 is essentially a lumen.Opening 72 may have a width “W4”, which is smaller than the widths W1and W2 of opening 62 of FIGS. 3A-3E. Although opening 76 is illustratedas having a small width W4, in other embodiments, ends 78A and 78B ofbody 74 may be in contact with one another or overlapping such that theopening does not define a gap, but ends 78A and 78B are not mechanicallycoupled and are moveable relative to one another. Openings 62, 72, and77 may be formed via cutting, slitting, molding, extruding, or otherwiseforming the openings.

Open sheath 60 (or other open sheaths described herein) may provide amulti-use sheath that may be reused more than once during a procedure bysimply putting the sheath 60 back over rod 30. Sheath 60 may thus beused to route lead 16 through more than one tunnel through tissue of thepatient or if the lead needs to be repositioned during the procedure. Asanother example, sheath 60 may permit the user to access channel 64formed by opening 62 anywhere along sheath 60. This may be a desirablefeature as every patient may have paths of different lengths and theuser may access channel 64 of sheath 60 in close proximity to theincision site. Sheath 60 may also provide handling advantages in that itmay be removed with only two hands, e.g., one to hold lead and the otherto hold handle of sheath 60.

FIG. 5 illustrates an angled view of the distal end of an example sheath80. Sheath 80 can include one or more of the structure and/orfunctionality of sheath 50 or 60 (and vice versa). Repetitivedescription of like numbered elements in other embodiments is omittedfor sake of brevity. Sheath 80 may, in one example, be used inconjunction with rod 30 of FIGS. 2A and 2B.

Sheath 80 may be substantially similar to sheath 60 of FIG. 3 exceptthat body 82 of sheath 80 does not include an opening 62. Instead, body82 forms a channel 84 that is a lumen accessible via the proximal end ordistal end of body 82. Body 82 of sheath 80 includes a score 83 thatextends along substantially the entire length along body 82 from thedistal end of body 82 of sheath 80 to the proximal end of body 82proximate a handle of the sheath. Unlike opening 62 of sheath 60, scoreline 83 does not create a gap or space along the circumference orcross-section of sheath 80 that extends along the length of body 82.Instead, score line 83 provides a weakened portion of body 82 that ismore susceptible to breaking or tearing than the remainder of body 82.When a user interacts with handle at the proximal end of body 82, e.g.,by applying oppositely directed forces to two sides of the handle, body82 of sheath 80 tears or breaks along score line 83 to permit removal oflead 16 from within channel 84.

Score line 83 may follow a substantially straight path from the distalend of body 82 of sheath 80 to the proximal end of body 82 of sheath 80.Alternatively, score 83 may follow other paths from the distal end ofbody 82 to the proximal end of body 82, such as a spiral path, ameandering path, or other path. Although illustrated as a score line 83,body 82 of sheath 80 may include weakened portions formed using othertechniques. For example, body 82 may be formed such that it issubstantially thinner along the path to for a weakened portion.Moreover, although a single score line 83 is illustrated in the exampleof FIG. 5, body 82 of sheath 80 may include more than one score line 83.For example, body 82 of sheath 80 may include a pair of score lines 83that are spaced 180 degrees circumferentially apart on body 82 of sheath80.

FIG. 6 illustrates an angled view of the distal end of an example sheath86. Sheath 86 can include one or more of the structure and/orfunctionality of sheath 50, 60, or 80 (and vice versa). Repetitivedescription of like numbered elements in other embodiments is omittedfor sake of brevity. Sheath 86 may, in one example, be used inconjunction with rod 30 of FIGS. 2A and 2B. Sheath 86 may besubstantially similar to sheath 60 of FIG. 3 or sheath 80 of FIG. 5except that body 88 does not include an opening 62 or a score line 83,respectively. Instead, body 88 of sheath 86 may be slit open to removelead 16 using a slitter or other means.

FIGS. 7A and 7B illustrate a distal end of the implant tool, such as theimplant tool formed by rod 30 and one of sheaths 50, 60, 80, or 86,being attached to a lead, such as defibrillation lead 16. Althoughdescribed in the context of sheath 50, any of the sheaths describedherein may be used in place of sheath 50. As illustrated in FIG. 7A,attachment feature 29 of lead 16 is placed within hook feature 36. Insome instances, sheath 50 may be pushed or slid toward the distal end ofrod 30 until body 52 of sheath 50 extends over the opening of hookfeature 36 thereby enclosing attachment feature 29 within hook feature36, as illustrated in FIG. 7B.

The position of sheath 50 may be adjusted on rod 30 to cover the openingof groove 60 of hook feature 36 may ensure that attachment feature 29 oflead 16 does not exit from groove 60 while being pulled through the pathformed in the tissue. Additionally, extending sheath 50 to cover theopening of groove 60 may prevent lip 43 or other portion of hook feature36 from catching on tissue or muscle when rod 30 pulled back through thepath formed in the tissue. After lead 16 is pulled through the path inthe tissue, the position of sheath 50 may again be adjusted, e.g., bypulling or sliding sheath 50 toward handle 32 of rod 30 such that body52 no longer extends over the opening of groove 60 and attachmentfeature 29 of lead 16 may be removed from groove 60. In this manner,sheath 50 may be placed in multiple positions on rod 30.

When positioned over the opening of groove 60, sheath 50 may be held inplace on shaft 34 of rod 30 by the interference fit described above. Inother instances, rod 30 or sheath 50 may designed to include a mechanismto hold sheath 50 in place when positioned over the opening of groove60. For example, stop 38 may be moveable such that when sheath 50 isadvanced to be positioned over groove 60 of hook feature 36, stop 38 maybe repositioned to keep sheath 50 from pushing back to the previousposition. Alternatively, handle 54 of sheath 50 may include a lockfeature, such as a tab, that can be pushed down to fill the spacebetween stop 38 and handle 54 when sheath 50 was pushed forward to coverthe opening of groove 60. In a further example, handle 54 itself may bedesigned to interact with handle 32 of rod 30 to position sheath 50 indifferent positions, as described in further detail with respect toFIGS. 11-13. As another example, the implant tool may include a separatestop feature that is added between handle 54 of sheath 50 and the stopfeature 38 of rod 30 when sheath 50 is advanced to cover the opening ofgroove 60. In any case, the element, whether it be a moveable stop, aportion of handle 54 of sheath 50 or a separate stop may be removed whensheath 50 is to no longer cover the opening of groove 60 of hook feature36.

Although FIG. 7 is illustrated and described in the context of hookfeature 36, rod 30 may include other attachment features. For example,rod 30 may include the attachment feature described in FIGS. 13A and 13Bor other attachment feature. Sheath 50 may be positioned to interactwith the lead 16 or the attachment feature of rod 30 to more securelyattach lead 16 to the implant tool.

FIGS. 8A-I illustrate an example method of implanting an implantablemedical lead, such as defibrillation lead 16, using an implant tool,such as the implant tool illustrated in FIGS. 2A and 2B. The techniquesillustrated in FIG. 8, however, may be performed using other implanttools described herein. As illustrated in FIG. 8A, a first incision 90is made at a location on the side of the torso of patient 12 and asecond incision 92 is made at a location near the center of the torso ofpatient 12. For example, first incision 90 may be made between theanterior axillary line and the posterior axillary line on the left sideof patient 12 and second incision 92 may be made near the xiphoidprocess of patient 12. However, first incision 90 and second incision 92may be made at other locations on the side and center of the torso,respectively. For example, second incision 92 may be offset to the leftor right of the xiphoid process of patient 12. As another example,second incision 92 may be made superior or inferior to the xiphoidprocess of the patient. Although described herein as first and secondincisions, the incisions may be made in any order.

Sheath 50 is placed over rod 30 (e.g., as show in FIG. 2B). The distalend of rod 30 is introduced into second incision 92 (as shown in FIG.8A) near the center of patient 12. The implant tool is advanced throughthe subcutaneous tissue from second incision 92 to first incision 90 (asshown in FIG. 8B). The implant tool may be advanced until the distal endof rod 30 and the distal end of sheath 50 exit through first incision 90or are close enough to first incision 90 such that the user may accesshook feature 36 (or other attachment feature) of rod 30. As describedabove with respect to FIG. 2, the distal end of rod 30 may be shaped toaid in tunneling through subcutaneous tissue from second incision 92 tofirst incision 90. For example, the distal end of rod 30 may be blunt,rounded, or otherwise shaped to enable a user to tunnel throughsubcutaneous tissue without damaging surrounding tissue or puncturingthrough the skin of patient 12.

The distal end of defibrillation lead 16 is attached to hook feature 36(or other attachment feature) of rod 30 (as illustrated in FIG. 8C). Forexample, attachment feature 29 may be placed in groove 60 of hookfeature 36 of rod 30 and sheath 50 may be advanced toward the distal endof rod 30 until sheath 50 covers the opening of hook feature 36 (asillustrated and described in detail with respect to FIGS. 7A and 7B).

Rod 30 is pulled toward second incision 92 thereby pulling lead 16through the subcutaneous path formed from the second incision 92 to thefirst incision 90 during the previous tunneling of rod 30 until rod 30and the distal end of lead 16 exit second incision 92 (as illustrated inFIG. 8D). Sheath 50 remains in place on shaft 34 of rod 30 during thepulling of the distal end of rod 30 from first incision 90 to secondincision 92. As described above, sheath 50 may be sized to form aninterference fit on shaft 34 of rod 30 to keep sheath 50 in place on rod34. Alternatively or additionally, the user may place a finger overhandle 54 of sheath 50 to keep sheath 50 in place on rod 34 or handle 54of sheath 50 may be locked into a position to hold sheath 50 in place onrod 34. Defibrillation lead 16 now partially resides within thesubcutaneous tissue from first incision 90 to second incision 92 withthe distal end of lead 16 extending out of second incision 92, theproximal end of lead 16 extending out of first incision 90, and theremainder of lead 16 is subcutaneously located in the tunnel formed byrod 30.

The steps illustrated in FIG. 8A-8C are for illustrative purposes onlyand should not be considered limiting of the techniques describedherein. The user may place defibrillation lead 16 along the path fromfirst incision 90 to second incision 92 in other manners. For example,rod 30 and sheath 50 may be advanced through the subcutaneous tissuefrom first incision 90 to second incision 92. In this case, anattachment feature of the proximal end of lead 16 may be placed withinan attachment feature of rod 30 (such as the attachment featuresdescribed in FIGS. 13A and 13B and the lead may be pulled from incision92 to incision 90 thereby placing a portion of lead 16 in thesubcutaneous path formed during the previous tunneling of rod 30.

The distal end of rod 30 and sheath 50 are then introduced into secondincision 92 near the center of the torso of patient 12 (as illustratedin FIG. 8E). Rod 30 is advanced subcutaneously superior from secondincision 92 substantially parallel to sternum 28 (as illustrated in FIG.8F). In the example illustrated in FIG. 8F, the path followed by rod 30is offset laterally to the left of the body of sternum 28 and the distalend of rod 30 is positioned near the second rib of patient 12. Such apath enables defibrillation lead 16 to be implanted such that thedefibrillation energy delivered via electrode 18 returns to the housingelectrode of ICD 14 through the left ventricle of heart 26. However, rod30 may be advanced along other paths. For example, the path followed byrod 30 may be offset from sternum 28 on the right side of sternum 28,over sternum 28 or other path depending on the anatomy of patient 12and/or location of ICD 14. As another example, distal end of rod 30 maybe positioned further superior or inferior depending on the location ofICD 14 relative to lead 16, placement of electrodes 18, 20 and 22 onlead 16, and other factors.

In instances in which sheath 50 and/or rod 30 include markings, the usermay determine the location of the distal end of rod 30 based on themarkings. In this manner, the user may utilize the markings on rod 30 orsheath 50 to aid in determining the location of the tunnel, e.g., howfar rod 30 has advanced within patient 12. The markings may also be usedto determine orientation of a distal feature (e.g., a bend or curve).This may be particularly useful in instances in which the patient isobese or the rod is tunneled underneath/below the sternum as thelocation of rod 30 may be more difficult to visualize.

While sheath 50 is held in place, rod 30 is pulled toward secondincision 92 until rod 30 exits the body of patient 12 thus leavingsheath 50 in place along the path within the body of patient 12 (asillustrated in FIG. 8G). The distal end of lead 16 is introduced intothe inner channel of sheath 50 and advanced along the inner channel ofsheath 50 from second incision 92 toward the distal end of sheath 50 (asillustrated in FIG. 8H).

Lead 16 is removed from the inner channel of sheath 50 and sheath 50 isremoved from the body of patient 12 while leaving defibrillation lead 16in place (as illustrated in FIG. 8I). Sheath 50 may be peeled off lead16 via opening 62 as described with respect to sheath 60 of FIG. 3,split and peeled off along a score line 83 or other weak portion of thesheath as described with respect to sheath 80 of FIG. 5, or slit using aslitter and peeled off as described with respect to sheath 86 of FIG. 6.In some instances, the distal end of lead 16 may include an anchoringmechanism to fixate the distal end of lead 16 in place near the superiorlocation (e.g., near the second or third rib). The anchoring mechanismmay include tines, a helix, or other anchoring mechanisms. In otherexamples, a third incision may be made toward the top of sternum 28proximate the desired location of the distal end of defibrillation lead16. In this case, rod 30 may be advanced subcutaneously from secondincision 92 to the third incision until distal end 38 exits through thethird incision. The distal end of defibrillation lead 16 would also beadvanced through sheath 50 until it is adjacent to the third incision.The distal end of defibrillation lead 16 may then be affixed to thedesired location proximate the third incision via a fixation mechanismseparate from defibrillation lead 16, e.g., sutures, staples, anchorsleeve, or the like, or built into defibrillation lead 16, e.g., tines,helix or other built in fixation mechanism.

The portion of defibrillation lead 16 proximate second incision 92 mayalso be affixed to the desired location proximate second incision 92 viaa fixation mechanism separate from defibrillation lead 16, e.g.,sutures, staples, anchor sleeve, or the like, or built intodefibrillation lead 16, e.g., tines, helix or other built in fixationmechanism.

A subcutaneous pocket may be created near first incision 90 and ICD 14may be placed within the subcutaneous pocket. A connector ofdefibrillation lead 16 is mechanically coupled to the connector block ofICD 14. The various incision and pockets may then be closed to completethe implant procedure.

The example method of implanting a lead illustrated in FIGS. 8A-I areexemplary in nature and should not be considered limiting of thetechniques described in this disclosure. The lead may be inserted usingthe implant tool of FIGS. 2A and 2B any of a number of ways, which isone of the advantages of such a tool. The implant tool may be used bythe user to pull lead 16 through the subcutaneous tissue (as describedabove with respect to FIGS. 8A-D) between any two incisions in anydirection or used by the user to push lead 16 through the subcutaneoustissue by creating the path, placing the sheath and pushing either theproximal or distal end of the lead through the sheath (similar to thesteps described above with respect to FIGS. 8E-I). In the example inwhich a third incision is made superior to the second incision, lead 16may be pulled from either the second incision to the third incision viaan attachment feature (e.g., 29) at the distal end of lead 16 or fromthe third incision to the second incision via an attachment feature(e.g., terminal pin of the connector) at the proximal end of lead 16. Insome instances, sheath 50 may be sized to have an interference fit withthe connector on the proximal end of lead 16 or by having an attachmentfeature on rod 30 configured to attach or couple to the connector orother portion of the proximal end of lead 16. As such, the implant toolhaving rod 30 and sheath 50 thus provides the user flexibility toperform lead insertion via either a pull method, a push method or acombination push and pull method.

In other examples, rod 30 may be introduced into second incision 92 andadvanced to create a tunnel or path that is not subcutaneous, butinstead is substernal. For example, rod 30 may be advanced under/belowthe sternum. Description of other locations are provided above withrespect to FIG. 1.

As described above with respect to FIG. 3, rod 30 and/or sheath 50 mayinclude markings 65 that coincide with features on lead 16, such asmarkings 65 that coincide with electrodes 18, 20 and 22 when the distalend of lead 16 is located at the distal end of sheath 50. In such cases,prior to tunneling or prior to creating incisions 90 and 92, the usermay place the implant tool on the skin of the patient such that themarkings of rod 30 and/or sheath 50 coincide with a desired location ofthe electrodes 18, 20 and 22 of lead 16 and place landmarks on the skinof patient 12 corresponding with a desired end point of a tunnel or adesired tunneling path that places the features (e.g., electrodes 18,20, and 22) of lead 16 at the desired location.

FIGS. 9A-9I illustrated another example method of implanting animplantable medical lead, such as defibrillation lead 16, using animplant tool, such as the implant tool illustrated in FIGS. 2A and 2B.The techniques illustrated in FIG. 9, however, may be performed usingother implant tools/kits described herein. As illustrated in FIG. 9A, afirst incision 90 is made at a location on the side of the torso ofpatient 12 and a second incision 92 is made at a location near thecenter of the torso of patient 12. For example, first incision 90 may bemade between the anterior axillary line and the posterior axillary lineon the left side of patient 12 and second incision 92 may be made nearthe xiphoid process of patient 12. However, first incision 90 and secondincision 92 may be made at other locations on the side and center of thetorso, respectively. For example, second incision 92 may be offset tothe left or right of the xiphoid process of the patient. As anotherexample, second incision 92 may be made superior or inferior to thexiphoid process of the patient. Although described herein as first andsecond incisions, the incisions may be made in any order.

Sheath 50 is placed over rod 30 (e.g., as show in FIG. 2B). The distalend of rod 30 is introduced into first incision 90 (as shown in FIG. 9A)on the left side of patient 12. Rod 30 and sheath 50 are advancedthrough the subcutaneous tissue from first incision 90 to secondincision 92 (as shown in FIG. 9B). The implant tool may be advanceduntil the distal end of rod 30 and the distal end of sheath 50 exitthrough first incision 90 or are close enough to first incision 90 suchthat the user may access sheath 50. As described above with respect toFIG. 2, the distal end of rod 30 may be shaped to aid in tunnelingthrough subcutaneous tissue from first incision 90 to second incision92. For example, the distal end of rod may be blunt, rounded, orotherwise shaped to enable a user to tunnel through subcutaneous tissuewithout damaging surrounding tissue or puncturing through the skin ofpatient 12.

While sheath 50 is held in place, rod 30 is pulled toward first incision90 until rod 30 exits the body of patient 12 thus leaving sheath 50 inplace within the body of patient 12 from the first incision 90 to thesecond incision 92 (as illustrated in FIG. 9C). The distal end of lead16 is introduced into the inner channel of sheath 50 near first incision90 and advanced along the inner channel of sheath 50 from first incision90 until the distal end of lead 16 exits out the distal end of sheath 50and second incision 92 (as illustrated in FIG. 9D). In other instances,the proximal end of lead 16 may be introduced into channel 58 nearincision 92 and advanced toward incision 90. Alternatively rod 30 andsheath 50 may be advanced from second incision 92 to first incision 90,rod 30 may be removed leaving sheath 50 in place and lead 16 may beadvanced either from incision 90 to incision 92 or from incision 92 toincision 90.

Lead 16 is removed from the inner channel of sheath 50 and sheath 50 isremoved from the body of patient 12 while leaving defibrillation lead 16in place (as illustrated in FIG. 9E). Sheath 50 may be peeled off lead16 via opening 62 as described with respect to sheath 60 of FIG. 3,split and peeled off along a score line 83 or other weak portion of thesheath as described with respect to sheath 80 of FIG. 5, or slit using aslitter and peeled off as described with respect to sheath 86 of FIG. 6.Defibrillation lead 16 now partially resides within the subcutaneoustissue from first incision 90 to second incision 92 with the distal endof lead 16 extending out of first incision 90, the proximal end of lead16 extending out of second incision 92, and the remainder of lead 16 issubcutaneously located in the tunnel formed by rod 30.

The same or a new sheath 50 is then replaced on shaft 34 of rod 30. Thedistal end of rod 30 and sheath 50 are then introduced into secondincision 92 near the center of the torso of patient 12 (as illustratedin FIG. 9E). Rod 30 is advanced subcutaneously superior from secondincision 92 (as illustrated in FIG. 9F). In instances in which sheath 50and/or rod 30 include markings, the user may determine the location ofthe distal end of rod 30 based on the markings.

While sheath 50 is held in place, rod 30 is pulled toward secondincision 92 until rod 30 exits the body of patient 12 thus leavingsheath 50 in place within the body of patient 12 (as illustrated in FIG.9G). The distal end of lead 16 is introduced into the inner channel ofsheath 50 near second incision 92 and advanced along the inner channelof sheath 50 from second incision 92 toward the distal end of sheath 50(as illustrated in FIG. 9H). When at the desired location, lead 16 isremoved from the inner channel of sheath 50 and sheath 50 is removedfrom the body of patient 12 (as illustrated in FIG. 9I). Sheath 50 maybe peeled off lead 16 via opening 62 as described with respect to sheath60 of FIG. 3, split and peeled off along a score line 83 or other weakportion of the sheath as described with respect to sheath 80 of FIG. 5,or slit using a slitter and peeled off as described with respect tosheath 86 of FIG. 6.

The example method of implanting a lead illustrated in FIGS. 9A-9I isexemplary in nature and should not be considered limiting of thetechniques described in this disclosure. In other examples, rod 30 maybe introduced into second incision 92 and advanced to create a tunnel orpath that is not subcutaneous, but instead is substernal. For example,rod 30 and sheath 50 may be advanced under/below the sternum.Description of other locations are provided above with respect to FIG.1.

As described above with respect to FIG. 3, rod 30 and/or sheath 50 mayinclude marking that coincide with features on lead 16, such as markingsthat coincide with electrodes 18, 20 and 22 when the distal end of lead16 is located at the distal end of sheath 50. In such cases, prior totunneling or prior to creating incisions 90 and 92, the user may placethe implant tool on the skin of the patient such that the markings ofrod 30 and/or sheath 50 coincide with a desired location of theelectrodes 18, 20 and 22 of lead 16 and place landmarks on the skin ofpatient 12 corresponding with a desired end point of a tunnel or adesired tunneling path that places the features (e.g., electrodes 18,20, and 22) of lead 16 at the desired location.

As illustrated in FIGS. 8 and 9, implant tools in accordance with thetechniques of this disclosure permit implantation of an implantablemedical lead any of a number of ways, which is one of the advantages ofsuch a tool. Although illustrated as being performed with the implanttool of FIGS. 2A and 2B, the techniques described above in FIGS. 8and/or 9 may be performed using any of the various tools describedherein.

FIG. 11 illustrates an example of another implant tool that includes arod 120 and a sheath 122. Repetitive description of like numberedelements in other embodiments is omitted for sake of brevity. Rod 120can include one or more of the structure and/or functionality of rod 30(and vice versa). Rod 120 is substantially similar to rod 30 of FIG. 2Aexcept that rod 120 has a different shaped handle 32′ and no stop 38.

Sheath 122 can include one or more of the structure and/or functionalityof sheath 50, 60, 80 and/or 86 (and vice versa) and may be used with anyof the rods described herein. Sheath 122 is substantially similar tosheath 50 of FIGS. 2 and 3 except that sheath 122 has a different handle126. Handle 126 of sheath 122 includes a plurality of grooves 128 spacedapart from one another. The distance between each of grooves 128 may beequal or different. FIG. 11 illustrates an enlarged view of handle 126of sheath 122. The example handle 126 of sheath 122 includes threegrooves 128, but handle 126 may include more or fewer grooves 128. Insome instances, handle 126 may include only a single groove. Grooves 128are shaped to conform to the curved portion of the proximal end ofhandle 32′ of rod 120. Handle 126 also includes a groove 129 thatreceives the proximal portion of sheath 122.

FIGS. 12A and 12B illustrate sheath 122 placed in two positions on rod120. FIG. 12A illustrates a first position in which the curved portionof the distal end of handle 32′ of rod 120 is positioned within the mostdistal groove 128 of handle 126. In this position, sheath 122 extendsalong the majority of the length of shaft 34, but does not cover theopening of hook feature 36.

When attachment feature 29 of lead 16 is placed within the groove ofhook feature 36, sheath 122 may be moved from the first position to asecond position illustrated in FIG. 12B. In the second position, thecurved portion of the distal end of handle 32′ of rod 120 is positionedwithin the subsequent groove 128 toward a proximal end of handle 126(the middle groove in FIG. 12). To place sheath 122 in the secondposition, the user may rotate sheath 122, push sheath 122 forwardslightly, and rotate sheath 122 back to its original orientation toplace handle 32′ within the second groove 128. In the second position,body 52 of sheath 122 covers the opening of hook feature 36 such thatattachment feature 29 of lead 16 does not exit hook feature 36 whilebeing pulled through a tunnel within body of patient 12.

In a further example, sheath 122 may be placed in a third position (notillustrated in FIGS. 12A and 12B) in which the curved portion of thedistal end of handle 32′ of rod 120 is positioned within the most distalgroove 128 of handle 126. In the third position, sheath 122 may extendbeyond the distal end of rod 120 and cover a portion of lead 16 (e.g., adistal end of lead 16 or a connector of lead 16), which may aid inpulling lead 16 through the subcutaneous tunnel. Alternatively, a distalend of sheath 50 may be sized to provide an interference fit with aconnector or other portion of lead 16.

FIGS. 13A and 13B illustrates a distal end of an alternative attachmentfeature of a rod 130. Rod 130 can include one or more of the structureand/or functionality of rod 30 and/or 120 (and vice versa). Rod 130 issubstantially similar to rod 30 and 120 except that rod 130 includes anattachment feature 132 at the distal end of rod 130. FIG. 13Aillustrates a side view of the distal end of rod 130 and FIG. 13Billustrates a cross-sectional view of the distal end of rod 130 takenfrom D-D′.

Attachment feature 132 of rod 130 includes a round recess 134 thatextends into a center of the distal end of rod 130 and a slit 136 thatextends across the diameter and into the distal end of rod 130. Therecess may extend within a non-centered portion of rod 130 (e.g., offsetto a side). In the example illustrated in FIG. 13A, slit 136 extendsfurther proximal along the length of the rod than recess 134, but thatneed not be the case. Round recess 134 is sized to interact with aterminal pin of a connector on the proximal end of lead 16. For example,the diameter of recess 134 may be sized to be equal to or slightlysmaller than the diameter of the terminal pin of a connector. In thismanner, the user of the implant tool may push the terminal pin of theconnector of lead 16 into recess 134, slightly expanding slit 136, whichcreates an interference fit with the terminal pin to couple lead 16 torod 130.

FIG. 14 illustrates a distal portion of an alternative rod 140. Rod 140can include one or more of the structure and/or functionality of rods30, 120, and/or 130 (and vice versa). Rod 140 is substantially similarto rods 30, 120, and/or 130 except that the distal end 142 of rod 140 isconstructed of a soft material. Rod 140 is constructed of two differentmaterials. A distal end 142 of rod 140 is constructed of a low durometermaterial, such as silicone, that is flexible. The remainder of rod 140is constructed of a higher durometer material, e.g., a high durometerpolymer or a metal, that is relatively stiff to permit tunneling throughsubcutaneous tissue or other structures of the body of patient 12.Toward the distal end 142 of rod 140, the higher durometer materialincludes a portion that has a smaller diameter than the proximal end ofrod 140 and extends within the lower durometer material of distal end142. A rod 140 with such a construction may be particularly useful whentunneling rod 140 underneath or below the sternum in the substernal,retrosternal, extravascular locations to avoid puncturing the pleuraand/or pericardium or others structure in those locations.

In the example illustrated in FIG. 14, the distal end 142 of rod 140 isa solid piece of low durometer material. In some instances, one or moreradiopaque markers may be added at one or more locations of the distalend 142 or a radiopaque additive maybe added to the polymer to allowvisualization of the distal end 142. For example, fluoroscopy may beused to determine the shape and deflection of the distal end 142 of rod140 during tunneling. This may be particularly useful when tunnelingunderneath or below the sternum in the substernal, retrosternal, orother extravascular locations.

FIG. 15 illustrates a distal portion of another alternative rod 150. Rod150 can include one or more of the structure and/or functionality ofrods 30, 120, 130 and/or 140 (and vice versa). The distal portion of rod150 is substantially to the distal portion of rod 140 except that thedistal end 152 of rod 150 is not constructed of a solid piece ofmaterial. Instead, distal end 152 forms an air cavity 154 within thesoft, low durometer material of distal end 152. Distal end 152 of rod150 is illustrated as including a plurality of radiopaque markers 156within the low durometer material. Radiopaque markers 156 may be placedsuch that a user may visualize the location and/or deflection of thedistal end 156, e.g., using fluoroscopy. This again may be particularlyuseful when tunneling underneath or below the sternum in the substernal,retrosternal, extravascular locations. In other instances, the materialused to form distal end may include a low durometer material that has aradiopaque additive.

Various examples have been described. These and other examples arewithin the scope of the following claims.

The invention claimed is:
 1. A system comprising: a medical lead,wherein the medical lead comprises: a lead body having a proximal endand a distal end, wherein the proximal end of the lead body isconfigured to connect to a medical device, and wherein the distal end ofthe lead body includes one or more electrodes; and an implant tool forimplanting the medical lead, wherein the implant tool comprises: a rodthat includes: a handle; a shaft having a proximal end adjacent to thehandle and a distal end, wherein the shaft is formed with a groove thatextends into the shaft to define an attachment feature toward the distalend of the shaft, the attachment feature configured to couple to themedical lead; and a sheath configured to be placed on the rod, whereinthe sheath includes a body having proximal end and a distal end, andfurther wherein the sheath is configured to be placed in multiplepositions along the rod including a first position in which the sheathdoes not interact with the attachment feature and second position inwhich the sheath does interact with the attachment feature.
 2. Thesystem of claim 1, wherein the attachment feature comprises a hookfeature defined by the groove that extends into the shaft and isconfigured to receive an attachment feature of the medical lead, whereinin the first position the sheath does not cover the hook feature and inthe second position the sheath does cover the hook feature.
 3. Thesystem of claim 2, wherein the shaft is formed with a groove thatextends into the shaft at an angle to define the hook feature.
 4. Thesystem of claim 1, wherein the attachment feature defined by the groovecomprises a recess that extends into the distal end of the shaft of therod, the recess being configured to receive and couple to a portion ofthe medical lead, wherein in the first position the sheath does notextend beyond the distal end of the shaft of the rod and in the secondposition the sheath does extend beyond the distal end of the shaft ofthe rod.
 5. The system of claim 4, wherein the recess is configured toreceive and couple to a terminal pin of a connector on the proximal endof the medical lead.
 6. The system of claim 5, wherein the shaft isformed with a groove that extends across a diameter of the distal end ofthe shaft and has a round recess that extends into a center of thedistal end of the rod and is sized to be equal to or slightly smallerthan a diameter of a terminal pin of a connector of the medical lead. 7.The system of claim 1, wherein the sheath includes a handle at theproximal end of the body, wherein the handle of the sheath is configuredto lock the sheath in the multiple positions.
 8. The of claim 7, whereinthe handle of the sheath includes at least a first groove and a secondgroove spaced apart from one another by a distance, wherein the firstand second grooves are shaped to receive a portion of the handle of therod such that when the portion of the handle of the rod is placed withinthe first groove the sheath is locked in the first position and when theportion of the handle of the rod is placed within the second groove thesheath is locked in the second position.
 9. The system of claim 1,wherein the multiple positions include a third position in which thesheath extends beyond the distal end of the shaft of the rod.
 10. Thesystem of claim 1, wherein the sheath includes an opening that extendsalong the body of the sheath from the proximal end to the distal end,wherein an inner channel of the sheath is accessible via the opening.11. The system of claim 1, wherein the sheath comprises a splittablesheath having one or more score lines.
 12. The system of claim 1,wherein the sheath comprises a slittable sheath.
 13. The system of claim1, wherein the shaft of the rod has a diameter that is greater than adiameter of the medical lead and the body of the sheath has an innerdiameter that is less than or equal to the diameter of rod such that thesheath and shaft of the rod create an interference fit.
 14. The systemof claim 13, wherein the sheath is held in the multiple positions alongthe shaft of the rod via the interference fit.
 15. The system of claim1, wherein at least one of the shaft of the rod and the body of thesheath includes one or more markings that identify locations thatcoincide with locations of features of the medical lead when the medicallead is placed within the sheath such that a distal end of the medicallead is located at the distal end of the body of the sheath.
 16. Thesystem of claim 15, wherein the one or more markings identify locationsthat coincide with locations of one or more electrodes of the medicallead when the medical lead is placed within the sheath such that adistal end of the medical lead is located at the distal end of the bodyof the sheath.
 17. The system of claim 16, wherein the one or moremarkings identify locations that coincide with locations of the one ormore electrodes of the medical lead when the medical lead is placedwithin the sheath such that a distal end of the medical lead is locatedat the distal end of the body of the sheath.
 18. The system of claim 1,wherein a first outer diameter of the shaft distal to the attachmentfeature is less than or approximately equal to a second outer diameterof the shaft proximal to the attachment feature.
 19. The system of claim1, wherein the distal end of the shaft of the rod is rounded.
 20. Asystem comprising: a medical lead; and an implant tool for implantingthe medical lead, the implant tool comprising: a rod that includes: ahandle; a shaft having a proximal end adjacent to the handle and adistal end, wherein the shaft of the rod has a diameter that is greaterthan a diameter of the medical lead, and wherein the shaft is formedwith a groove that extends into the shaft to define an attachmentfeature toward the distal end of the shaft, the attachment featureconfigured to couple to the medical lead; and a sheath configured to beplaced on the rod, wherein the sheath includes a body having proximalend and a distal end, the body of the sheath having an inner diameterthat is less than or equal to the diameter of the rod such that thesheath and shaft of the rod create an interference fit, and furtherwherein the sheath is configured to be placed in multiple positionsalong the rod including a first position in which the sheath does notinteract with the attachment feature and second position in which thesheath does interact with the attachment feature.
 21. The system ofclaim 20, wherein the sheath is held in the multiple positions along theshaft of the rod via the interference fit.
 22. A system comprising: arod that includes: a handle; a shaft having a proximal end adjacent tothe handle and a distal end, wherein the shaft is formed with a groovethat extends into the shaft to define an attachment feature toward thedistal end of the shaft, the attachment feature configured to couple tothe medical lead; a sheath configured to be placed on the rod, whereinthe sheath includes a body having proximal end and a distal end, andfurther wherein the sheath is configured to be placed in multiplepositions along the rod including a first position in which the sheathdoes not interact with the attachment feature and second position inwhich the sheath does interact with the attachment feature; and animplantable medical lead that includes one or more electrodes along adistal portion of the medical lead, wherein at least one of the shaft ofthe rod and the body of the sheath includes one or more markings thatidentify locations that coincide with locations of the one or moreelectrodes of the medical lead when the medical lead is placed withinthe sheath such that a distal end of the medical lead is located at thedistal end of the body of the sheath.